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PubMed1975

Recurrent contact dermatitis caused by mercury in amalgam dental fillings.

A metal worker had repeated episodes of contact dermatitis over a period of years. Patch tests with 5% ammoniated mercury were strongly positive but occupational contact could not be proved. Recurrence of the dermatitis one day after amalgam dental fillings had been made and again one year later, this time without new fillings, raised the possibility that it was due to the old amalgam fillings. Removal of all the amalgam fillings resulted in a new outbreak of severe dermatitis; during the 5 years ensuing there has been no recurrence. This case history suggests that contact dermatitis may be caused by not only the mercury in new fillings but also by that in old fillings.

Adult↗
PubMed2003

Evaluation of the long-term corrosion behavior of dental amalgams: influence of palladium addition and particle morphology.

OBJECTIVES: The purpose of this investigation was to evaluate the long-term corrosion behavior of experimental amalgams as a function of particle morphology and palladium content. METHODS: Samples of four experimental high copper amalgams were prepared according to ADA specifications. Two of them had the same chemical composition but one had lathe cut particles (LCP) and the other had spherical particles (SP). The two others had spherical powders with an addition of 0.5 wt% of palladium (SP 0.5) and 1 wt% of palladium(SP 1) for the other. Corrosion resistance was evaluated by electrochemical techniques in Ringer's solution in a thermostated cell at 37 degrees C for samples aged 5, 8, 12, 16 months and 10 years. Potentiokinetic curves were drawn and the potential and the current density corresponding to the first anodic peak were registered. RESULTS: For all the amalgam samples the corrosion behavior improves over the 10-year period. SP samples exhibit a better behavior than LCP. Palladium addition improves corrosion behavior as compared to samples without palladium. No real difference is found regarding the amount of palladium between 0.5 and 1%. The potentials progress from a range between 0 and 20 mV/SCE to a range of 60-80 after 10 years. The stabilization of the potential begins after only 16 months. Except for the LCP, all the values converge to the same level of 80 mV/SCE. SIGNIFICANCE: The addition of no more than 0.5 wt% Palladium in a high copper amalgam powder improves the corrosion behavior of the amalgam up to a period of 10 years. The potential of the first anodic peak increases for each amalgam, probably in relation to the evolution of the structure of the material. Clinically, it is of interest to consider the good electrochemical behavior of older restorations when contemplating the repair or replacement of such fillings. At the same time, galvanic current can occur when a new amalgam restoration is placed in contact with an old one even if the same amalgam is used. In this situation, the new filling will be anodic and its degradation will be accelerated. The evaluation of the corrosion behavior of dental amalgams has to take into account the age of the samples.

Copper↗
PubMed1986

The development of mercury- and selenium-containing deposits in the kidneys following implantation of dental amalgams in guinea pigs.

Examination of light microscopical sections of the kidneys of guinea pigs with chronic exposure to mercury as the result of the breakdown of subcutaneous implants of powdered dental amalgam demonstrated the development of black, refractile deposits in the cytoplasm and nuclei of cells in both the straight and convoluted portions of the proximal tubule. The more numerous cytoplasmic deposits were of a particulate nature with dimensions of approximately 1 microgram. The nuclear deposits, which appeared later but which were relatively more common in longer-term animals, took the form of prominent inclusions, 1 to 3 micrograms in diameter. The ratio of nuclear to cytoplasmic deposits was higher in animals receiving high copper as compared with conventional amalgam. At electron microscopical level, the cytoplasmic deposits were seen to consist of collections of fine particles within lysosomes. Similar deposits were also found in far smaller numbers in lysosomes in collecting duct cells. The nuclear inclusions in proximal tubular cells were made up of closely packed electron dense granules. X-ray microanalysis showed both lysosomal and nuclear deposits to contain mercury and selenium. The association of mercury with selenium, which was present in the animals' diet at low levels, probably aided the microscopical visualisation of the deposits.

Animals↗
PubMed1983

Methylation of mercury from dental amalgam and mercuric chloride by oral streptococci in vitro.

The capacity of the oral bacteria Streptococcus mitior, S. mutans and S. sanguis to methylate mercury was investigated in vitro. Mercuric chloride and pulverized dental amalgam in distilled water, respectively, were used as sources of mercury. Methylmercury was found in the bacterial cells of all three tested strains. The results indicate that organic mercury compounds may be formed in the oral cavity.

Dental Amalgam↗
PubMedDate not supplied

Immune factors, dental amalgam, and low-dose exposure to mercury in Swedish adolescents.

Occupational high-dose exposure to metallic mercury can cause immune disturbances in sensitive individuals. Whether low-dose exposure to inorganic mercury from dental amalgam has this effect in humans is one of the issues related to the concept of oral galvanism and is supported by results of animal studies. This study explored some cellular immune factors (B- and T-lymphocytes, T4, T8, monocytes, neutrophilic, eosinophilic, and basophilic granulocytes, and large unstained cells) and some humoral immune factors (immunoglobulins IgG, IgG1, IgG2, IgG3, IgG4, IgA, IgM, IgE, albumin, alfa-1-antitrypsin, orosomucoid, haptoglobin, and antinuclear antibodies) in 41 healthy 15-y-old schoolchildren. The relationship between these factors and amalgam fillings and mercury concentrations in plasma (P-Hg) were investigated. A low, but significant correlation (r = 0.40, p < .05) was found between the number of amalgam surfaces and the P-Hg values, which were low for both sexes (median value = 1.8 nmol/l). There was no significant influence of the number of amalgam surfaces or P-Hg on the immune factors tested, except random findings. The girls had significantly higher values of T8, IgG, and IgG1 than the boys.

Adolescent↗
PubMed1977

Creep of dental amalgam and its phases.

The intention of the study was to evaluate creep as a function of temperature and stress, and to determine creep rate of compounds with a composition equivalent to the gamma, gamma1, and gamma2 phases in dental amalgam. The results were consistent with a creep model in which the deformation takes place in the gamma1 phase, and is dominated by glide pileups of dislocations in grain boundaries.

Dental Amalgam↗
PubMed2006

Surface change of dental amalgam after treatment with 10% carbamide peroxide.

The aim of this study was to explore the effect of bleaching agents on the release of metal ions and change in physical and chemical characteristics of amalgams. Amalgam surface changes resulting from bleaching on amalgam were assessed with inductively coupled plasma atomic emission spectrophotometer, an automatic mercury analyzer, a colorimeter, and atomic force microscopy. Analysis of the release of metal ions indicated that the bleaching agent caused more copper, tin, and mercury ions to be released into the immersion solution. Furthermore, metal ion release increased progressively as immersion time was increased from 42 to 84 hours. Morphological examination revealed no significant effects of the 10% carbamide peroxide bleaching agent on the surface morphology of any of the amalgams tested. These results demonstrated that bleaching using 10% carbamide peroxide did not adversely affect the two types of amalgam tested. In other words, a 10% carbamide peroxide bleaching agent can be safely used on a short-term basis in dentist-monitored bleaching of the dental amalgam.

Analysis of Variance↗
PubMed1990

[Crack path in dental amalgams].

The need of amalgam to resist fracture becomes a more evident necessity when restoration margins are taken into consideration. Marginal microcracks permit bacteria to pass beneath the restoration resulting in cement base dessalution, secondary caries and pulp inflammation. Fracture toughness of amalgam is usually studied indirectly from the maximum force required to fracture the amalgam, during compressive, tensile or bend stresses, through its ability to deform plastically or its surface hardness. Important information on fracture toughness of amalgams can be also taken from metallographic studies of their microstructures, during or after the formation of a crack. This study was planned to evaluate the microcracks produced on the surface of different amalgams, with a Vickers pyramid head of a hardness tester and their relation to the different phases of the amalgam structure. Seven amalgams were studied: Amalcap-F, Tytin, Cupralloy, Ana-2000 and three experimental combinations of them, in order to have in the same amalgam different alloy particles, for evaluation purposes. The result showed that the structure elements, that mainly assist crack formation and propagation, are voids and gamma 2-phase, while elements that resist fracture are alloy particles (gamma-phase) in conventional amalgams, eutectic spheres in admixed high copper amalgams and eta'-phase crystals in single melt high copper amalgams.

Dental Amalgam↗
PubMed1982

Modification of a simple method for determination of gamma-2 phase of dental amalgam.

Evidence is presented for the formation of a tin-citrate ligand complex that severely limits the shelf life of the SnCl2-citric acid solutions used to standardize the reaction of the gamma 2 phase of dental amalgam with PMA. Early ligand complex formation probably accounts for the lack of linearity in the SN+2-PMA reaction seen at low SN+2 concentrations and is a potential source of error in the original, analytical method outlined by Kropp. Substitution of 1% HCl (0.27N) for 5% citric acid throughout the procedure is proposed. It was noted, however, that Sn+2in 1% HCl undergoes oxidation to Sn++ and thus limits shelf life of these solutions.

Chemical Phenomena↗